Brushless dc motor configuration for a power tool

ABSTRACT

A power tool with a combined printed circuit board (PCB) having a doughnut shape and located coaxially with a motor shaft. The combined PCB is secured to a heat sink on one end of the motor and a metal end piece is positioned on an opposite end of the motor. The metal end cap and heat sink are secured to one another via fasteners to provide a rigid coupling. A tabbed end piece is provided between the heat sink and the motor stator and is also secured into place via the fasteners. The tabbed end piece includes wire support tabs that provide strain relief to motor coil leads. The wire support tabs extend axially from circumferential locations of the tabbed end piece and include channels to guide the motor coil leads to solder contact points on the combined PCB.

RELATED APPLICATIONS

The present application claims priority to, and is a continuation of, U.S. Non-provisional patent application Ser. No. 14/295,703, filed on Jun. 4, 2014, which claims priority to U.S. Provisional Patent Application No. 61/832,012, filed on Jun. 6, 2013, the entire contents of each of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to brushless motor power tools.

BACKGROUND

Power tool motors can generally be grouped into two categories: brushed motors and brushless motors. In a brushed motor, motor brushes make and break electrical connection to the motor due to rotation of the rotor. In a brushless motor power tool, such as power tool 100 of FIG. 1, switching elements are selectively enabled and disabled by control signals from a controller to selectively apply power from a power source to drive the brushless motor. The power tool 100 is a brushless hammer drill having a housing 102 with a handle portion 104 and motor housing portion 106. The power tool 100 further includes an output unit 107, torque setting dial 108, forward/reverse selector 110, trigger 112, battery interface 114, and light 116.

FIG. 2 illustrates a simplified block diagram 120 of the brushless power tool 100, which includes a power source 122 (e.g., a battery pack), Field Effect Transistors (FETs) 124, a motor 126, hall sensors 128, a motor control unit 130, user input 132, and other components 133 (battery pack fuel gauge, work lights (LEDs), current/voltage sensors, etc.). The Hall sensors 128 provide motor information feedback, such as motor rotational position information, which can be used by the motor control unit 130 to determine motor position, velocity, and/or acceleration. The motor control unit 130 receives user controls from user input 132, such as by depressing the trigger 112 or shifting the forward/reverse selector 110. In response to the motor information feedback and user controls, the motor control unit 130 transmits control signals to accurately control the FETs 124 to drive the motor 126. By selectively enabling and disabling the FETs 124, power from the power source 122 is selectively applied to the motor 126 to cause rotation of a rotor. Although not shown, the motor control unit 130 and other components of the power tool 100 are electrically coupled to the power source 122 such that the power source 122 provides power thereto.

SUMMARY

In one embodiment, the invention provides a power tool including a housing and a brushless direct current (DC) motor within the housing. The brushless DC motor includes a rotor and a stator, wherein the rotor is coupled to a motor shaft to produce a rotational output. The power tool further includes an annular metal end piece, a heat sink, and a printed circuit board (PCB). The annular metal end piece is positioned at a first end of the brushless DC motor, while the heat sink is positioned at a second end of the brushless DC motor opposite the first end such that the brushless DC motor is between the heat sink and the annular metal end piece. The heat sink and the annular metal end piece are secured together to clamp the brushless DC motor, thereby rigidly coupling the heat sink to the brushless DC motor. The PCB is positioned at the second end of the brushless DC motor and is secured to the heat sink.

In another embodiment, the invention provides a power tool comprising: housing and a brushless direct current (DC) motor within the housing. The brushless DC motor includes a rotor and a stator, wherein the rotor is coupled to a motor shaft to produce a rotational output. The power tool further includes an annular metal end piece, a heat sink, threaded fastening elements, and a printed circuit board (PCB). The annular metal end piece is positioned at a first end of the brushless DC motor, while the heat sink is positioned at a second end of the brushless DC motor opposite the first end. The brushless DC motor is positioned between the heat sink and the annular metal end piece and has an axial length. The threaded fastening elements extend the axial length of the brushless DC motor and secure the heat sink to the annular metal end piece. The PCB is positioned at the second end of the brushless DC motor and is secured to the heat sink. The PCB includes a Hall sensor, power switching elements (e.g., field effect transistors), and a through-hole through which the motor shaft extends.

In another embodiment, the invention provides a power tool including a housing and a brushless direct current (DC) motor within the housing. The brushless DC motor includes a rotor and a stator, wherein the rotor is coupled to a motor shaft to produce a rotational output. The power tool further includes an annular metal end piece, an end cap, a heat sink, threaded fastening elements, and a printed circuit board (PCB). The annular metal end piece is positioned at a first end of the brushless DC motor. The end cap is positioned over and secured to the annular metal end piece at the first end of the brushless DC motor. The heat sink is positioned at a second end of the brushless DC motor opposite the first end such that the brushless DC motor is between the heat sink and the annular metal end piece. The heat sink and the annular metal end piece are secured together to clamp the brushless DC motor, thereby rigidly coupling the heat sink to the brushless DC motor. The brushless DC motor has an axial length, and the threaded fastening elements extend the axial length and secure the heat sink to the annular metal end piece. The PCB is positioned at the second end of the brushless DC motor and is secured to the heat sink. The PCB includes a Hall sensor, power switching elements, and a through-hole through which the motor shaft extends.

Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a brushless power tool.

FIG. 2 illustrates a block diagram of a brushless power tool.

FIGS. 3A, 3B, and 4 provide additional views of the brushless power tool of FIG. 1.

FIG. 5 illustrates a Hall sensor board.

FIGS. 6-7 illustrate a brushless power tool having a combined surfboard PCB.

FIGS. 8A-C provide additional views of the combined surfboard PCB.

FIGS. 9-11 illustrate another brushless power tool having a combined surfboard PCB.

FIGS. 12-14 illustrate another brushless power tool having a combined surfboard PCB.

FIG. 15 illustrates a brushless power tool having a combined doughnut PCB.

FIGS. 16A-B show the combined doughnut PCB of the power tool of FIG. 15.

FIGS. 17A-B show a combined Hall and FET PCB of the power tool of FIG. 15.

FIGS. 18A-B show a combined control PCB of the PCB stack.

FIGS. 19A-G illustrate a process for attaching a Hall and FET PCB and heat sink to a brushless motor.

FIG. 20 illustrates a wire wrap technique for a brushless motor.

FIG. 21 illustrates another combined Hall sensor and FET PCB for use with a brushless power tool.

FIGS. 22A-C illustrate alternative locations for a control PCB on the brushless power tool of FIG. 15.

FIGS. 23A-B illustrate an alternate brushless motor configuration.

FIGS. 24A-D illustrate components of the alternate brushless motor configuration of FIGS. 23A-B.

FIGS. 25A-B further illustrate components of the alternate brushless motor configuration of FIGS. 23A-B.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.

FIG. 3A illustrates a cross section of the brushless power tool 100 of FIG. 1, and FIG. 3B illustrates select components of the power tool 100. The power tool 100 includes separate printed circuit boards (PCBs) for various components of the power tool 100. More particularly, the power tool 100 includes a control printed circuit board (PCB) 136, a power PCB 138, a forward/reverse PCB 140, a Hall sensor PCB 142, and a light-emitting diode (LED) PCB 144. Also illustrated in FIG. 3A is a drive mechanism 148 for transmitting the rotational output of the motor 126 to the output unit 107, and a cooling fan 149 rotated by the motor 126 and used to provide a cooling air flow over components of the power tool 100.

As shown in FIG. 4, the control PCB 136 is positioned at the base of the tool 100 between the handle portion 104 and the battery interface 114, which may also be referred to as a terminal block portion. The control PCB 136 includes the motor control unit 130, which is operable to receive user input, to receive motor information feedback, and to control the FETs 124 to drive the motor 126. The control PCB 136 is electrically and physically coupled to terminal blades 150. When a battery pack (i.e., the power source 122) is coupled to the battery interface 114, terminals of the battery pack are received by and electrically coupled to the terminal blades 150. The number of terminal blades can vary based on the type of hand-held power tool. However, as an illustrative example, terminal blades 150 can include a battery positive (“B+”) terminal, a battery negative (“B−”) terminal, a sense or communication terminal, and an identification terminal. As shown in FIG. 4, the terminal blades 150 have tabs 152 that extend upward through the control PCB 136. The tabs 152 may be directly soldered to the control PCB 136, eliminating the need for additional power wires. The motor control unit may use the communication terminal to communicate with a battery pack, allowing the battery pack to communicate whether it is capable of discharging to the power tool 100 and other information.

The power PCB 138 includes the FETs 124, which are connected to and controlled by the motor control unit 130 of the control PCB 136. As discussed above, the FETs 124 are also electrically coupled to the power source 122 and the motor 126. In some embodiments, the FETs 124 are directly coupled (i.e., directly physically and/or thermally coupled) to the heat sink 154 (e.g., directly on the heat sink, via copper tracings on the power PCB 138, etc.). In other embodiments, the FETs 124 are not directly coupled to the heat sink 154, but are in a heat transfer relationship with the heat sink 154.

The forward/reverse PCB 140 includes a forward/reverse switch that is operated by the forward/reverse selector 110, which has three positions: forward, reverse, and neutral. The positions may be shifted between by moving the forward/reverse selector/shuttle 110 in a direction normal to the plane of the drawing of FIG. 1 (i.e., in/out of the page). When the forward/reverse selector 110 is shifted between these three positions, the selector 110 switches the forward/reverse switch of the forward/reverse PCB 140, which provides a signal to the motor control unit 130. When the trigger 112 is depressed, the motor control unit 130 causes the motor 126 to rotate clockwise, rotate counterclockwise, or not rotate (e.g., in neutral) based on the position of the selector 110.

The Hall sensor PCB 142 includes hall sensors 128 to detect one or more of the rotational position, velocity, and acceleration of the motor 126. The Hall sensor PCB 142 is electrically coupled to the control PCB 136 to provide the outputs of the Hall sensors 128. As shown in FIGS. 3B and 5, the Hall sensor PCB 142 includes a through-hole 156 through which a motor shaft/spindle 158 passes. Each Hall sensor 128 outputs a pulse when magnet of the rotor rotates across the face of that Hall sensor 128. Based on the timing of the pulses from the Hall sensors 128, the motor control unit 130 can determine the position, velocity, and acceleration of the rotor. The motor control unit 130, in turn, uses the motor feedback information to control the FETs 124.

The light-emitting element (LED) PCB 144 includes the light 116, which may be a light emitting diode (LED). The LED PCB 144 is electrically coupled to the control PCB 136 such that the motor control unit 130 is operable to selectively enable and disable the light 116. The motor control unit 130 may enable the light 116 when the trigger 112 is depressed and/or when a separate light switch on the housing 102 is activated by the user to selectively enable/disable the light 116 independent of the trigger 112. The motor control unit 130 may further include a delay timer such that the light 116 remains illuminated for a period of time after the trigger 112 or light switch is depressed or released.

The motor control unit 130 is implemented by the control PCB 136, which includes motor control unit 130 includes combinations of hardware and software that control operation of the power tool 100. For example, the control PCB 136 includes, among other things, a processing unit (e.g., a microprocessor, a microcontroller, or another suitable programmable device), a memory, input units, and output units. The processing unit includes, among other things, a control unit, an arithmetic logic unit (“ALU”), and a plurality of registers, and is implemented using a known computer architecture, such as a modified Harvard architecture, a von Neumann architecture, etc. The processing unit, the memory, the input units, and the output units, as well as the various modules connected to or part of the control PCB 136 are connected by one or more control and/or data buses. In some embodiments, the control PCB 136 is implemented partially or entirely on a semiconductor (e.g., a field-programmable gate array [“FPGA”] semiconductor) chip, such as a chip developed through a register transfer level (“RTL”) design process.

The memory of the control PCB 136 includes, for example, a program storage area and a data storage area. The program storage area and the data storage area can include combinations of different types of memory, such as read-only memory (“ROM”), random access memory (“RAM”) (e.g., dynamic RAM [“DRAM”], synchronous DRAM [“SDRAM”], etc.), electrically erasable programmable read-only memory (“EEPROM”), flash memory, a hard disk, an SD card, or other suitable magnetic, optical, physical, or electronic memory devices. The processing unit is connected to the memory and executes software instructions that are capable of being stored in a RAM of the memory (e.g., during execution), a ROM of the memory (e.g., on a generally permanent basis), or another non-transitory computer readable medium such as another memory or a disc. Software included in the implementation of the battery pack can be stored in the memory of the controller. The software includes, for example, firmware, one or more applications, program data, filters, rules, one or more program modules, and other executable instructions. The processing unit is configured to retrieve from memory and execute, among other things, instructions related to the control of the battery pack described herein. The processing unit can also store various battery pack parameters and characteristics (including battery pack nominal voltage, chemistry, battery cell characteristics, maximum allowed discharge current, maximum allowed temperature, etc.). In other constructions, the control PCB 136 includes additional, fewer, or different components.

The motor control unit 130 may further be in communication with one or more sensors to monitor temperature, voltage, current, etc., of the power tool 100 and an attached battery pack. The motor control unit 130 may also include protection capabilities based on a variety of preset or calculated fault condition values related to temperatures, currents, voltages, etc., associated with the operation of the hand-held power tool.

The various interconnections of the power tool 100 between the control PCB 136, the power PCB 138, the forward/reverse PCB 140, the Hall sensor PCB 142, and the light-emitting element (LED) PCB 144 can lead to a complex and space-consuming wiring layout within the housing 102.

FIGS. 6-7 illustrate a brushless power tool 200, which has similarities to power tool 100, but has a different electronics layout. The layout of power tool 200 has reduced wiring and assembly complexity relative to the power tool 100. Additionally, the more compact and efficient layout of the power tool 200 enables additional flexibility in design, such as by allowing different handle and body dimensions and shapes. Elements of the power tool 200 similar to those of the power tool 100 are similarly numbered to simplify the description thereof.

Rather than a separate control PCB 136, power PCB 138, forward/reverse PCB 140, and LED PCB 144, the power tool 200 includes a combined surfboard PCB 202 incorporating the functionality of each. The combined surfboard PCB 202 includes the FETs 124 of the power PCB 138, the light 116 of the LED PCB 144, the motor control unit 130 of the control PCB 136, and a forward/reverse switch 203 of the forward/reverse PCB 140 (see FIG. 8C). Accordingly, in place of wires running through the housing 102 to interconnect the various PCBs, the connections are made via conductors on the combined surfboard PCB 202.

As illustrated, the combined surfboard PCB 202 has an elongated shape, with a length more than twice its width. The combined surfboard PCB 202 has a rear portion adjacent to the motor 126 and a front portion adjacent to a trigger 112. The Hall sensor PCB 142 is positioned above and generally perpendicularly (i.e., within 15 degrees of a perpendicular) to the combined surfboard PCB 202).

Moreover, the combined surfboard PCB 202 is positioned near the fan 149, such that cooling air flow 204 passes over the FETs 124 and other components of the combined surfboard PCB 202. The fan 149 operates to draw the cooling air flow 204 from the combined surfboard PCB 202 towards the fan 149, or, as illustrated, to push the cooling air flow 204 from the fan 149 over the combined surfboard PCB 202. Furthermore, air inlets and outlets are formed on the housing 102 to provide an inlet and outlet path for the cooling air flow 204.

The components of the combined surfboard PCB 202 are exposed. In other words, the combined surfboard PCB 202 is not encapsulated or potted within the housing 102 and is not protected against fluid within the housing 102 from reaching the FETs 124 or motor control unit 130. Exposing the combined surfboard PCB 202 improves the thermal management of the components thereon. For example, the cooling air flow 204 is operable to reach and cool the FETs 124, enabling the FETs 124 to operate at higher current levels and the motor 126 to operate at higher power levels and generate higher torque for longer periods of time.

As shown in FIGS. 8A-C, the FETs 124 are mounted in a generally flat orientation on the combined surfboard PCB 202. In contrast, the FETs 124 of the power tool 100 are mounted on the power PCB 138 in a perpendicular orientation. The combined surfboard PCB 202 also has mounted thereon a heat sink 206 on a side opposite of the FETs 124 to provide cooling of the FETs 124. The heat sink 206 is thermally coupled to the FETs 124 and includes heat sink fins 208 to improve the heat sinking capabilities of the heat sink 206. In some instances, one or more additional heat sinks are positioned on the same side as the FETs 124, such that the FETs 124 and the combined surfboard PCB 202 are located between the heat sink 206 and the one or more additional heat sinks. The one or more additional heat sinks are thermally coupled to the FETs 124 to provide additional thermal management. A front portion 209 of the bottom surface of the combined surfboard PCB 202 includes the light 116 and the forward/reverse switch 203 mounted thereon. The FETs 124 are mounted on a rear portion 210 of the bottom surface of the combined surfboard PCB 202. The heat sink 206 is mounted on the rear portion 210 of the top surface of the combined surfboard PCB 202. The Hall sensor PCB 142 is above the surfboard PCB 202 and, taken together, generally form an upside-down “T” shape.

Additionally, the combined surfboard PCB 202 is centrally located within the power tool 200 above the trigger 112, but below the motor 126 and drive mechanism 148. FIG. 7 illustrates a region 211 considered above the trigger 112 and below the motor 126. “Below the motor” does not require that the combined surfboard PCB 202 be directly below the motor 126, but, rather, below a line extending parallel to the bottom surface of the motor 126. Accordingly, a shortened combined surfboard PCB 202 that does not extend rearward in the tool 200 such that it is, in part, directly under the motor 126 as shown in FIG. 7 can still be considered “below the motor.” Similarly, “above the trigger” does not require that the combined surfboard PCB 202 be directly above the trigger, but, rather, within the region 211.

The central location allows relatively short wire connections between several components of the power tool 200. Furthermore, the exposed, unencapsulated nature of the combined surfboard PCB 202 further enables more flexibility in connection points to components thereon. That is, wires can reach components of the combined surfboard PCB 202 generally directly, rather than through limited ingress/egress ports of an encapsulation housing, allowing shorter and more direct wire connections. More particularly, the combined surfboard PCB 202 is near the Hall sensor PCB 142, the light 116, the trigger 112, the forward/reverse switch 203, and terminals of the motor 126. For instance, FIG. 8A illustrates the short wires 212 connecting the Hall sensor PCB 142 and the combined surfboard PCB 202. The wires 212 may be flexible or rigid and are connected generally at a middle portion of the combined surfboard PCB 202. Additionally, as shown, the wires 212 have a length less than a diameter of the motor 126, less than one-fourth of the length of the combined surfboard PCB 202, and less than a diameter of the Hall sensor PCB 142. Although a top surface of the combined surfboard PCB 202 is substantially parallel to the longitudinal axis of the motor shaft 158, the combined surfboard PCB 202 is angled slightly downward with respect to the motor shaft 158 from the motor side to the output side of the power tool 200. As illustrated in FIG. 6-7, the combined surfboard PCB 202 has a slight downward angle of less than 5 degrees with respect to the motor shaft 158.

In some embodiments, the forward/reverse selector 110 includes a magnet mounted therein and the combined surfboard PCB 202 includes a forward/reverse Hall sensor (not shown) in place of the forward/reverse switch 203. The forward/reverse Hall sensor detects movement of the embedded magnet when the forward/reverse selector 110 is moved, and a signal indicating the position or movement of the forward/reverse selector 110 is provided to the motor control unit 130.

The combined surfboard PCB 202 includes an exemplary component layout. In some embodiments, various components, such as one or more of the FETs 124, are mounted on a different portion of the combined surfboard PCB 202 (e.g., top instead of bottom surface, front instead of rear portion, etc.).

In some embodiments, the power tool 200 is a (non-hammer) drill/driver power tool that includes a similar electronics layout, housing, motor, etc., but includes a different drive mechanism 148 having no hammer mechanism.

FIGS. 9-11 illustrate a brushless impact wrench power tool 250 including an impact output unit 252. The impact wrench is another type of hand-held power tool used for generating rotational output, but includes an impact mechanism 254 that differs from the hammer-style drive mechanism 148 of the power tools 100 and 200.

The power tool 250 includes a similar layout as the power tool 200. More particularly, the power tool 250 includes a housing 256 with a handle portion 258 and motor housing portion 260. The motor housing portion 260 houses a motor 126 and is positioned above the handle portion 258. The handle portion 258 includes the battery interface 114 for coupling to a battery pack. Additionally, the power tool 250 includes the combined surfboard PCB 202 and Hall sensor PCB 142. The layout of power tool 250 has reduced wiring and assembly complexity relative to the power tool 100. Additionally, the more compact and efficient layout of the power tool 250 enables additional flexibility in design, such as by allowing different handle and body dimensions and shapes. Elements of the power tool 250 similar to those of the power tools 100 and 250 are similarly numbered to simplify the description thereof.

FIGS. 12-14 illustrate a brushless impact driver power tool 270 including an impact output unit 272. The impact driver power tool 270 is another type of hand-held power tool used for generating rotational output that includes an impact mechanism 274 similar to the impact mechanism 254. Additionally, the power tool 270 includes a clip 276 for hanging the power tool 270 on various items, such as on a hook or tool belt.

The power tool 270 includes a similar layout as the power tools 200 and 250. More particularly, the power tool 270 includes a housing 278 with a handle portion 280 and motor housing portion 282. The motor portion 282 houses a motor 126 and is positioned above the handle portion 280. The handle portion 280 includes the battery interface 114 for coupling to a battery pack. Additionally, the power tool 270 includes the combined surfboard PCB 202 and Hall sensor PCB 142. The layout of power tool 270 has reduced wiring and assembly complexity relative to the power tool 100. Additionally, the more compact and efficient layout of the power tool 270 enables additional flexibility in design, such as by allowing different handle and body dimensions and shapes. Elements of the power tool 270 similar to those of the power tools 100 and 270 are similarly numbered to simplify the description thereof.

Although the physical layout of the combined surfboard PCB 202 may be generally similar for each of the power tools 200, 250, and 270, the particular software and hardware of the motor control unit 130 and ratings of electrical components and FETs 124 may vary and be optimized for each tool.

FIG. 15 illustrates another brushless impact wrench power tool 300 including the impact output unit 252 and impact mechanism 254, and having a battery pack 301 attached to the battery interface 114. Elements of the power tool 300 similar to the previously described power tools are similarly numbered to simplify the description thereof.

The layout of power tool 300, like that of the power tools 200, 250, and 270, has reduced wiring complexity and reduced costs relative to the power tool 100. However, the power tool 300 has a different PCB layout in that the combined surfboard PCB 202 is not included. Rather, the components of the combined surfboard PCB 202 are positioned on (generally) doughnut-shaped PCBs near the motor. Separate PCBs similar to the LED PCB 144 and forward/reverse PCB 140 may be provided in the power tool 300 for inclusion and support of the light 116 and switch 203, respectively.

More specifically, as shown in FIGS. 16A-B, the power tool 300 includes a Hall and FET PCB 302 and a control PCB 304 stacked on the motor 126 and having a hole through which the motor shaft 158 passes. The Hall and FET PCB 302 is kept separated from the control PCB 304 by spacers 305 (also referred to as standoffs). The Hall and FET PCB 302 includes the Hall sensors 128 and the FETs 124, while the control PCB 304 includes the motor control unit 130. Additionally, a heat sink 306, also with a generally doughnut or ring shape, is secured between the Hall and FET PCB 302 and the motor 126. The heat sink 306 is generally used to transfer heat away from the FETs 124.

FIGS. 17A-B illustrate the Hall and FET PCB 302 in greater detail. The Hall and FET PCB 302 has a generally circular shape with a through-hole 308 in the center. A motor shaft 158, as well as a motor bushing 309 (see, e.g., FIG. 21), pass through the through-hole 308. The Hall and FET PCB 302 has two generally flat mounting surfaces: a first face 310 (see FIG. 17A) and a second face 312 (see FIG. 17B). The FETs 124 are mounted on the Hall and FET PCB 302 in a flat orientation. Similarly, the control PCB 304 has a through-hole 314 and two generally flat mounting surfaces: a first face 316 (see FIG. 18A) and a second face 318 (see FIG. 18B). The FETs 124 are shown mounted on the first face 310, while the Hall sensors 128 may be mounted on the second face 318, staggered at approximately 120 degrees, to be closer to the rotor magnets similar to the PCB 142 (see, e.g., FIG. 5). The control PCB 304 further includes control PCB mounting holes 319. The control PCB 304 and Hall and FET PCB 302 are located coaxially about the motor shaft 158 and the faces 310, 312, 316, and 318 are generally parallel to each other. The PCBs 302 and 304 are secured to an end of the motor 126. By locating FETs 124 with Hall sensors 128 on a single Hall and FET PCB 302 secured to the end of the motor 126, the Hall and FET PCB 302 is able to receive a large amount of air flow 204 for cooling in addition to reducing the internal wiring of the power tool 300.

The Hall and FET PCB 302 further includes Hall and FET PCB mounting holes 320, motor lead pads 322, and copper bus bars 324. The copper bus bars 324 allow for additional space on the Hall and FET PCB 302 to be used for other features such as high current traces. Accordingly, rather than occupying space on the Hall and FET PCB 302, the copper bus bars 324 jump above the Hall and FET PCB 302. In alternative embodiments, traces on the Hall and FET PCB 302 are used instead of the copper bus bars 324.

The Hall and FET PCB mounting holes 320 allow metal standoffs 305 (see FIG. 16A-B) of the heat sink 306 to pass through the Hall and FET PCB 302. The metal standoffs 305 provide spacing between the PCBs 302 and 304 and allow the control PCB 304 to be attached to the heat sink 306. The metal standoffs 305 receive control PCB mounting screws inserted through mounting holes 319 of the control PCB 304 to secure the control PCB 304 to the heat sink 306. In some embodiments, the control PCB mounting screws secure both the control PCB 304 and the Hall and FET PCB 302 to the heat sink 306.

Furthermore, in some embodiments, Hall and FET PCB mounting holes 320 may be used for both allowing metal standoffs 305 of the heat sink 306 to pass through the Hall and FET PCB 302 and for securing the Hall and FET PCB 302 to the heat sink 306. Tightly securing the Hall and FET PCB 302 to the heat sink 326 allows for heat to dissipate from the Hall and FET PCB 302 to the heat sink 306 more easily and minimizes vibration between the Hall and FET PCB 302 and the motor 126. In other embodiments of the invention, the number of mounting holes 319 and 320 and their location on the PCBs 302 and 304 are varied. Furthermore, in other embodiments, the general shape of the PCBs 302 and 304 is varied.

FIGS. 19A-G illustrate a process for attaching the motor 126, Hall and FET PCB 302, and heat sink 306 together. FIG. 19A illustrates a motor stator 330 of the motor 126 with plastic end caps 332 and 334 at each end of the motor stator 330, respectively, and six motor leads 336 that are stripped down to the plastic end cap 334. Wire support features 338 are part of the plastic end cap 334 and will be used to properly guide the motor leads 336, as explained below. FIG. 19B illustrates the heat sink 306 placed on the plastic end cap 334 of the motor stator 330. The metal standoffs 305 of the heat sink 306 may be used for mounting the control PCB 304 and/or locating the Hall and FET PCB 302 in some embodiments.

FIG. 19C illustrates the heat sink 306 fastened to the motor stator 330 using heat sink mounting screws 340. Heat sink mounting clips 342 are attached to an end of the motor stator 330 opposite the end where the heat sink 306 is attached. The heat sink mounting screws 340 are threadingly engaged with heat sink mounting standoffs of the heat sink 306 and the heat sink mounting clips 342 to secure the heat sink 306 to the motor stator 330. In some embodiments the number and location of heat sink mounting elements are varied.

After securing the heat sink 306, the motor leads 336 are then bent downward to fit within the wire support features 338 as shown in FIG. 19D. Wrapping the motor leads 336 around the wire support features 338 relieves strain on the motor leads 336 before they are soldered to the Hall and FET PCB 302. In some embodiments, glue can also be applied to the motor leads 336 to secure them to the heat sink 306.

FIG. 19E illustrates a heat sink pad 344 placed on top of the heat sink 306. The heat sink pad 344 is a thin, electrical insulator with high thermal conductivity. These characteristics allow the heat sink pad 306 to electrically isolate the metal heat sink 306 from the Hall and FET PCB 302 while still allowing heat from the Hall and FET PCB 302 to dissipate via the heat sink 306.

FIG. 19F illustrates the Hall and FET PCB 302 placed on top of the heat sink pad 344 and heat sink 306. The motor leads 336 align with the openings of the motor lead pads 322, and the metal standoffs 305 of the heat sink 306 pass through the Hall and FET PCB mounting holes 320. To ensure contact between the Hall and FET PCB 302 and the heat sink 306, downward force is applied to the Hall and FET PCB 302.

As illustrated in FIG. 19G, the motor leads 336 are soldered to the motor lead pads 322 to create solder joints 345, which not only electrically connect the motor leads 336 to the Hall and FET PCB 302, but also mechanically attach the two components together. After creating the solder joints 345, the motor leads 336 are cut near the motor lead pads 322. As described above, in addition to the solder joints 345, the Hall and FET PCB 302 can be secured to the heat sink 306 (which is secured to the motor 126) using Hall and FET PCB mounting screws.

After securing the Hall and FET PCB 302 to the motor 126 and heat sink 306 combination, the control PCB 304 is then secured to the heat sink 306 with the Hall and FET PCB 302 positioned between the heat sink 306 and the control PCB 304. The control PCB 304 is secured to the heat sink 306 using control PCB mounting screws received by the standoffs 305.

FIG. 20 illustrates the end of the motor stator 330 opposite from the end having the Hall and FET PCB 302. This view of the motor stator 330 illustrates a wire crossover design, which wraps a wire behind the plastic end cap 332. Wrapping the wires of the motor stator 330 around the plastic end cap 332 allows them to travel 180 degrees from one pole to the opposite pole of the motor stator 330 in an efficient manner. The wrapped wires 346 are on top of a ledge portion 348, which wraps around the motor stator 330, and are radially outside of tab portions 349 that extend up from the ledge portion 348. As illustrated, at no point are three wires located at the same circumferential position and stacked along the ledge portion 348. Rather, at most, two wires are stacked, allowing a reduced height of the tab portions 349 and overall length of the motor stator 330.

In some embodiments, the control PCB 304 is not located adjacent to the Hall and FET PCB 302 about the motor shaft 158, and the metal standoffs 305 do not pass through the Hall and FET PCB 302. Rather, the length of the metal standoffs 305 is reduced such that they terminate at the surface of the Hall and FET PCB 302. The reduced metal standoffs 305, which no longer provide spacing functionality, then receive Hall and FET PCB mounting screws to secure the Hall and FET PCB 302 to the heat sink 306 and motor 126 combination, as shown in FIG. 21.

In embodiments in which the control PCB 304 is not located adjacent to the Hall and FET PCB 302, the control PCB 304 may be referred to as the control PCB 304 a. The control PCB 304 a may be located in several locations within the power tool 300. The Hall and FET PCB 302 is coupled to the control PCB 304 a via cable connector 350 and a ribbon cable (not shown).

FIGS. 22A-C illustrate exemplary locations within the power tool 300 that the control PCB 304 a may be positioned. In FIG. 22A, similar to the power PCB 138 of the power tool 100, the control PCB 304 a is located in the handle portion 258 of the power tool 300. In FIG. 22B, similar to the combined surfboard PCB 202, the control PCB 304 a is located above the trigger 112 and handle portion 258, but below the motor 126 and impact mechanism 254. In FIG. 22C, similar to the control PCB 136 of the power tool 100, the control PCB 304 a is located below the handle portion 258 and above the battery interface 114.

Although FIGS. 15-22 are described with respect to an impact wrench power tool 300, the various layout and motor assembly described may be implemented in other types of power tools, such as a non-hammer drill/driver power tool, a hammer drill/driver power tool (see, e.g., FIGS. 1-9) and an impact driver power tool (see, e.g., FIGS. 12-14).

The above power tools (e.g., power tools 200, 250, 270, and 300) are described as cordless, battery-powered tools. The battery packs, such as battery pack 301, used to power these power tools may be, for instance, 18 volt lithium ion type battery packs, although battery packs with other battery chemistries, shapes, voltage levels, etc. may be used in other embodiments. In some embodiments, these power tools are corded, AC-powered tools. For instance, in place of the battery interface 114 and battery pack, the power tools include an AC power cord coupled to a transformer block to condition and transform the AC power for use by the components of the power tools. These AC-powered tools may also include one of the above-described layouts including one of the combined surfboard PCB layouts and doughnut PCB layouts.

FIGS. 23A and B illustrate an alternate brushless motor configuration 399 that may be used in place of the configuration shown in, for instance, FIGS. 15 and 22A-C. The brushless motor configuration 399 includes a metal end piece 400 and a tabbed end piece 402 on opposite ends of the motor 126. The metal end piece 400 and tabbed end piece 402 are more clearly illustrated in FIGS. 24C and 24A, respectively. The metal end piece 400 and tabbed end piece 402 have a generally ring-like shape. In the brushless motor configuration 399, the metal end piece 400 is used in place of the plastic end cap 332 shown in FIG. 19A. The plastic material of the plastic end cap 332 may be subject to deformation or movement at elevated temperatures when the motor 126 is in operation. The movement can include relative movement between the PCB 302 and motor coils, which can lead to an increased risk of fracture to leads 336.

Use of the metal end piece 400 enables a rigid connection of the PCB 302 to the motor 126. The metal end piece 400 and heat sink 306 include through-holes 404 and 405, respectively, for receipt of threaded fasteners 406, which secure the stator 330 and tabbed end piece 402 therebetween. The threaded fasteners 406 may be thread-forming screws. The heat sink 306 is coupled to the metal end piece 400 via the threaded fasteners 406 to clamp the brushless DC motor between the heat sink 306 and the metal end piece 400, thereby rigidly coupling the heat sink 306 to the motor 126. The PCB 302 is rigidly coupled to the heat sink 306 via screws 408; thus, rigidly coupling the heat sink 306 to the brushless DC motor 126 rigidly couples the PCB 302 to the motor 126.

In some embodiments, the threaded fastener 406 is secured to the metal end piece 400 with a nut or the like. The motor configuration 399 includes four through-holes 404 and fasteners 406 spread apart by approximately 90 degrees along the circumference of the motor 126. The PCB 302 is coupled to the heat sink 306 via six screws 408 spaced apart by approximately 60 degrees. The heat sink 306 is annular and includes six through-holes 410 for receiving screws 408, as shown in greater detail in FIG. 24D. The motor 126 has an axial length 409, and the threaded fasteners 406 extend the axial length 409 along the outer circumference of the motor 126.

The brushless motor configuration 399 also includes the wire crossover design as described with reference to FIG. 20. For instance, the brushless motor configuration 399 includes an end cap 407 having the ledge portion 348, tab portions 349, and wrapped wires 346. At no point are more than two wires stacked at the same circumferential position along the ledge portion 348. The end cap 407 is more clearly illustrated in FIG. 24B and FIGS. 25A-B. The end cap 407 includes two locator tabs 450 that are received in two respective recesses 452 of the metal end piece 400. The locator tabs 450 each further include a snap tab 454 extending over the outer circumference of the metal end piece 400 in the axial direction of the motor 126, and then radially inward (i.e., towards the motor shaft). The radially inward portion of the snap tab 454 resides in a channel 456 on the outer circumference of the motor 126 (see FIGS. 23A-B). The snap tab 454 flexes radially outward to allow axial insertion of the metal end piece 400 into an annular recess 458 of the end cap 407. Once the metal end piece 400 is axially inserted, the snap tab 454 returns to the radially inward position to securely couple the end cap 407 to the metal end piece 400 (see FIG. 25A).

As shown in FIG. 24A, the tabbed end piece 402 (also referred to as a second end cap) includes wire support tabs 412. The wire support tabs 412 provide strain relief to reduce the stress on the leads 336 and, thereby, reduce the risk of damage or breakage of the leads 336. The leads 336 are wrapped around the wire support tabs 412 before reaching the soldering contact points (solder joints 345) on the PCB 302. The wire support tabs 412 extend axially toward the PCB 302 from outer circumferential points of the tabbed end piece 402. The wire support tabs 412 include channels 414 for receiving the leads 336. After passing through one of the channels 414, the lead 336 is bent at an approximately ninety degree angle toward the soldering contact points on the PCB 302 (see FIG. 23A). The motor configuration 399 includes three sets of wire support tabs 412, one tab 412 per lead 336, spread around the tabbed end piece 402. The wire support tabs 412 are spaced apart by approximately 120 degrees along the circumference of the tabbed end piece 402.

Thus, the invention provides, among other things, a layout design and assembly of brushless power tools. Various features and advantages of the invention are set forth in the following claims. 

What is claimed is:
 1. A power tool comprising: a housing; a brushless direct current (DC) motor within the housing, wherein the brushless DC motor includes a rotor and a stator, wherein the rotor is coupled to a motor shaft to produce a rotational output; an annular metal end piece positioned at a first end of the brushless DC motor; a heat sink positioned at a second end of the brushless DC motor opposite the first end, wherein the brushless DC motor is positioned between the heat sink and the annular metal end piece; threaded fastening elements securing the heat sink to the annular metal end piece, wherein the brushless DC motor has an axial length, and the threaded fastening elements extend the axial length of the brushless DC motor from the first end to the second end; and a printed circuit board (PCB) positioned at the second end of the brushless DC motor and secured to the heat sink, wherein the PCB includes a Hall sensor, power switching elements, and a through-hole through which the motor shaft extends.
 2. The power tool of claim 1, wherein the heat sink includes a shaft through-hole through which the motor shaft extends.
 3. The power tool of claim 1, further comprising an end cap positioned over the annular metal end piece at the first end of the brushless DC motor.
 4. The power tool of claim 3, wherein the annular metal end piece includes a recess and the end cap includes a locator tab configured to fit in the recess and thereby align the end cap and the metal end piece.
 5. The power tool of claim 4, wherein the locator tab further includes a snap tab to secure the end cap to the metal end piece, the snap tab extending axially over the metal end piece then radially inward.
 6. The power tool of claim 1, further comprising a second end cap positioned between the heat sink and the second end of the brushless DC motor.
 7. The power tool of claim 6, wherein the second end cap includes wire support tabs, each wire support tab having a channel that guides a portion of a motor lead wire extending to the PCB.
 8. A power tool comprising: a housing; a brushless direct current (DC) motor within the housing, wherein the brushless DC motor includes a rotor and a stator, wherein the rotor is coupled to a motor shaft that extends along an axial length of the brushless DC motor to produce a rotational output; an annular metal end piece positioned at a first end of the brushless DC motor; a heat sink positioned at a second end of the brushless DC motor opposite the first end, wherein the brushless DC motor is positioned between the heat sink and the annular metal end piece; fastening elements securing the heat sink to the annular metal end piece, wherein the fastening elements extend along the axial length of the brushless DC motor and bridge a gap between the heat sink and the annular metal end piece; and a printed circuit board (PCB) positioned at the second end of the brushless DC motor and secured to the heat sink.
 9. The power tool of claim 8, wherein the PCB includes a Hall sensor, power switching elements, and a through-hole through which the motor shaft extends.
 10. The power tool of claim 8, wherein the heat sink includes a shaft through-hole through which the motor shaft extends.
 11. The power tool of claim 8, further comprising an end cap positioned over the annular metal end piece at the first end of the brushless DC motor.
 12. The power tool of claim 11, wherein the annular metal end piece includes a recess and the end cap includes a locator tab configured to fit in the recess and thereby align the end cap and the metal end piece.
 13. The power tool of claim 12, wherein the locator tab further includes a snap tab to secure the end cap to the metal end piece, the snap tab extending axially over the metal end piece then radially inward.
 14. The power tool of claim 8, further comprising a second end cap positioned between the heat sink and the second end of the brushless DC motor.
 15. The power tool of claim 14, wherein the second end cap includes wire support tabs, each wire support tab having a channel that guides a portion of a motor lead wire extending to the PCB.
 16. The power tool of claim 8, wherein the fastening elements include a first fastening element having a first length that is greater than an axial length of the heat sink in the direction that the motor shaft extends.
 17. A motor assembly comprising: a brushless direct current (DC) motor within a housing, wherein the brushless DC motor includes a rotor and a stator, wherein the rotor is coupled to a motor shaft that extends along an axial length of the brushless DC motor to produce a rotational output; an annular metal end piece positioned at a first end of the brushless DC motor; a heat sink positioned at a second end of the brushless DC motor opposite the first end, wherein the brushless DC motor is positioned between the heat sink and the annular metal end piece; fastening elements securing the heat sink to the annular metal end piece, wherein the fastening elements extend along the axial length of the brushless DC motor and bridge a gap between the heat sink and the annular metal end piece; and a printed circuit board (PCB) positioned at the second end of the brushless DC motor and secured to the heat sink.
 18. The motor assembly of claim 17, wherein the PCB includes a Hall sensor, power switching elements, and a through-hole through which the motor shaft extends.
 19. The motor assembly of claim 17, wherein the heat sink includes a shaft through-hole through which the motor shaft extends.
 20. The motor assembly of claim 17, wherein the fastening elements include a first fastening element having a first length that is greater than an axial length of the heat sink in the direction that the motor shaft extends. 